Proteoglycans are ubiquitous components of connective tissues where they occur as major components of the extracellular matrix of these tissues. Cartilage proteoglycans have been the most thoroughly studied and as such they have served as a useful model for understanding proteoglycan structure and function in other more complex connective tissue matrices. Recent advances made the use of recombinant DNA technologies have significantly advanced our knowledge as to primary amino acid sequence data of the core proteins of a large number of these connective tissue proteoglycans. These studies have allowed researchers to categorize several classes of the proteoglycans into gene- and structure/function-related families. It is now possible to use these newly developed molecular biological technologies to perform a wide variety of cell biological and metabolic studies examining several hitherto unattainable problems relating to proteoglycan structure function and metabolism. In spite of these advances, we still know very little regarding the biological significance of the inherent heterogeneity and polydispersity that is observed in the wide variety of proteoglycans found in different connective tissues. This heterogeneity is largely a result of a complex array of post-translational modifications that occur in these molecules during both their biosynthesis, and also in their organization and turnover within the extracellular matrix. At present immunological approaches offer possibly the best means of studying the biological mechanism causing the inherent proteoglycans heterogeneity observed in vivo. Over the past ten years this laboratory has pioneered the field in the use of monoclonal antibody technology to study proteoglycan structure, function and metabolism in health and disease. In the past funding period we produced and characterized several new monoclonal antibodies that were used to identity the differential expression of subtle structural components in connective tissue proteoglycans during growth and development and in pathology, e.g. osteoarthritis. In this current proposal we plan to continue to develop and use monoclonal antibody technology to address problems relating to proteoglycan structure and function in connective tissues. The focus of this proposal will be proteoglycan heterogeneity in cartilage. Our specific aims to achieve this objective are (i) to further characterize currently existing monoclonal antibodies against proteoglycan epitopes; (ii) to produce a panel of new monoclonal antibodies with specificities directed against domain-, species- and tissue-specific epitopes on different proteoglycan subpopulations; (iii) to produce monoclonal antibodies directed against "neo-epitopes" on proteoglycans that occur as a result of metalloproteinase degradation of these molecules, and (iv) to use the antibodies generated in the previous three specific aims to study mechanisms involved in proteoglycan heterogeneity.